Method and system for establishing emergency call

ABSTRACT

A method for establishing an emergency call includes: if an emergency call request message sent by a User Equipment (UE) contains an Internet Protocol Multimedia Subsystem Public User Identity (IMPU) in a TEL URI format, a Proxy-Call Session Control Function entity (P-CSCF) generates an IMPU in a Session Initiation Protocol (SIP) URI format according to the IMPU in the TEL URI format, sends both IMPUs to a Public Safety Answering Point (PSAP), and receives an emergency callback initiated by the PSAP. The PSAP initiates the emergency callback according to one of the two IMPUs. A system for establishing an emergency call includes a UE, a P-CSCF and a PSAP. The PSAP can always acquire the IMPU in the TEL URI format and the IMPU in the SIP URI format of the UE, and initiate an emergency callback to the UE according to the IMPU in the SIP URI format.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2007/070320, filed Jul. 19, 2007. This application claims thebenefit of Chinese Application No. 200610103398.7, filed Jul. 21, 2006.The disclosures of the above applications are incorporated herein byreference.

FIELD

The present disclosure relates to emergency service technologies, andmore particularly, to a method and system for establishing an emergencycall.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Internet Protocol Multimedia Subsystem (IMS) is a subsystem supportingIP multimedia service, and is proposed by the 3rd Generation PartnershipProject (3GPP) in Revision 5 (R5). The main feature of the IMS is usingof Session Initiation Protocol (SIP) and the supports of accessindependence. The IMS is a multimedia control or call control platformin Packet-Switched (PS) domain. The IMS supports session multimediaservices and non-session multimedia services, and provides a commonservice platform for the future multimedia application.

The emergency call is a special voice service function in mobiletelecommunication system. Even in the case that call barring is set in amobile terminal and that Subscriber Identity Module (SIM) is notinserted in the mobile terminal, when a user dials some special numbersuch as 110, 119 or 120, the call will be forwarded to the correspondingPublic Safety Answering Point (PSAP) such as police stations, firedepartments and first aid centers as long as the mobile terminal islocated in the area covered by the mobile network. Therefore, emergencyaid service can be provided to users round the clock. Operations of theentire system are implemented jointly by telecom operators, firedepartments, hospitals and the like.

Conventionally, the emergency call is implemented in theCircuit-Switched (CS) domain. While more and more networks adopt the IPtechnology, the PS domain begins to support the emergency call servicegradually, and use the IMS system to control call signaling for theemergency session. The emergency call service provided by the IMS domainis called IMS Emergency Call, for short, IMS-EMER.

Subscriber identity in the IMS system is called IMS Public Identity(IMPU), and the IMPU is used when an IMS user requests to communicatewith others. The IMPU is in SIP Uniform Resource Identifier (SIP URI)format or in Telephone Uniform Resource Identifier (TEL URI) format. TheSIP URI takes the form of sip: user@domain, where the “user” stands foruser name and the “domain” stands for domain name. The TEL URI takes theform of tel: number, where the “number” is generally internationalstandard telephone number, i.e., E.164 number.

FIG. 1 is a flowchart of a conventional method for emergency call in anIMS domain. The method is described in further detail below.

In Block 101, a User Equipment (UE) sends an emergency call requestmessage to a proxy call session control function entity (P-CSCF), theemergency call message contains an emergency call identifier. Further,the P-Preferred-Identity header of the emergency call request messagecontains an IMPU in TEL URI format or in SIP URI format.

In Block 102, the P-CSSF receives the emergency call request message,then, the P-CSCF checks whether the IMPU of the UE contained in theemergency call request message is in the TEL URI format or in the SIPURI format. If the IMPU is in the TEL URI format, Block 103 isperformed. If the IMPU is in the SIP URI format, Block 105 is performed.

In Block 103, the P-CSCF checks whether the IMPU in the TEL URI formatis valid. The IMPU in the TEL URI format is contained in the emergencycall request message. If the IMPU in the TEL URI format is valid, Block104 is performed; if the IMPU in the TEL URI format is not valid, theemergency call fails, and the process is terminated.

In Block 104, the P-CSCF generates a P-Asserted-Identity header in theemergency call request message, and the IMPU in the TEL URI format iscontained in the P-Asserted-Identity header. Meanwhile, the P-CSCFdeletes the P-Preferred-Identity header from the emergency call requestmessage, and then sends the emergency call request message to anEmergency-CSCF (E-CSCF), and Block 106 is performed.

In Block 105, the P-CSCF generates a P-Asserted-Identity header in theemergency call request message, and generates an IMPU in the TEL URIformat according to the IMPU in the SIP URI format contained in theemergency call request message. The IMPU in the TEL URI format and theIMPU in the SIP URI format are both contained in the P-Asserted-Identityheader. Meanwhile, the P-CSCF deletes the P-Preferred-Identity headerfrom the emergency call request message, and then sends the emergencycall request message to the E-CSCF.

In Block 106, the E-CSCF forwards the emergency call request message toPSAP after receives the emergency call request message from the P-CSCF.

In Block 107, the PSAP receives the emergency call request message, andsaves a UE calling identifier contained in the emergency call requestmessage, i.e., saves the IMPU in the TEL URI format in theP-Asserted-Identity header, or saves the IMPU in the TEL URI format andthe IMPU in the SIP URI format in the P-Asserted-Identity header.

When the PSAP determines to initiate an emergency callback to the UE, ifthe PSAP detects that the PSAP is located in the CS domain, the PSAPsends an emergency callback request message to the UE according to theIMPU in the TEL URI format, the emergency callback request message issent to the UE via S-CSCF and P-CSCF in turn; if the PSAP detects thatthe PSAP is located in the PS domain, the PSAP checks whether the PSAPsaves the IMPU in the SIP URI format. If the PSAP saves the IMPU in theSIP URI format, the PSAP sends the emergency callback request message tothe UE via S-CSCF and P-CSCF in turn according to the IMPU in the SIPURI format. If the PSAP does not save the IMPU in the SIP URI format,the PSAP performs telephone number mapping (ENUM) function to find theIMPU in the SIP URI format according to the IMPU in the TEL URI formatsaved in the PSAP, and then sends the emergency callback request messageto the UE via S-CSCF and P-CSCF in turn according to the IMPU in the SIPURI format.

SUMMARY

In one embodiment, the disclosure includes a method for establishing anemergency call including:

if a Proxy-Call Session Control Function entity (P-CSCF) receives anemergency call request message sent by a User Equipment (UE) and detectsthat the emergency call request message contains an Internet ProtocolMultimedia Subsystem Public User Identity (IMPU) in a Telephone UniformResource Identifier (TEL URI) format, the P-CSCF generates an IMPU in aSession Initiation Protocol (SIP) URI format according to the IMPU inthe TEL URI format; and sends the IMPU in the TEL URI format and theIMPU in the SIP URI format to a Public Safety Answering Point (PSAP);and receives an emergency callback initiated by the PSAP to the UE. Theemergency callback is initiated by the PSAP according to one of the IMPUin the TEL URI format and the IMPU in the SIP URI format.

In various embodiments, the disclosure includes a system forestablishing an emergency call including:

a User Equipment (UE), adapted to send an emergency call request messagecontaining an Internet Protocol Multimedia Subsystem Public UserIdentity (IMPU) of the UE; a Proxy-Call Session Control Function(P-CSCF), adapted to detect that the IMPU of the UE is in a TelephoneUniform Resource Identifier (TEL URI) format, generate an IMPU in aSession Initiation Protocol (SIP) URI format according to the IMPU inthe TEL URI format, and send the IMPU in the SIP URI format and the IMPUin the TEL URI format; and a Public Safety Answering Point (PSAP),adapted to initiate an emergency callback to the UE according to one ofthe IMPU in the SIP URI format and the IMPU in the TEL URI format whichare received from the P-CSCF.

In various embodiments, the disclosure includes a Proxy-Call SessionControl Function entity (P-CSCF) includes:

an Internet Protocol Multimedia Subsystem Public User Identity (IMPU)reception and detection module, adapted to receive an IMPU sent by UserEquipment (UE), and send the IMPU to be converted if the IMPU isdetected in a Telephone Uniform Resource Identifier (TEL URI) format;and an IMPU format conversion module, adapted to generate an IMPU in aSession Initiation Protocol (SIP) URI format according to the IMPU inthe TEL URI format sent by the IMPU reception and detection module, andsend the IMPU in the SIP URI format and IMPU in the TEL URI format to aPublic Safety Answering Point (PSAP).

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a flowchart of a conventional method for establishing anemergency call in an IMS domain of prior art;

FIG. 2 is a flowchart of a method for establishing an emergency call inan IMS domain in accordance with an embodiment;

FIG. 3 is a schematic diagram illustrates a system for an emergency callin an IMS domain in accordance with an embodiment; and

FIG. 4 is a schematic diagram of a P-CSCF in accordance with anembodiment.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

Reference throughout this specification to “one embodiment,” “anembodiment,” “specific embodiment,” or the like in the singular orplural means that one or more particular features, structures, orcharacteristics described in connection with an embodiment is includedin at least one embodiment of the present disclosure. Thus, theappearances of the phrases “in one embodiment” or “in an embodiment,”“in a specific embodiment,” or the like in the singular or plural invarious places throughout this specification are not necessarily allreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in any suitable manner inone or more embodiments.

In practice, if the PSAP is located in the PS domain and does not savethe IMPU in the SIP URI format of the UE, the PSAP needs to perform theENUM function to find the IMPU in the SIP URI format according to thesaved IMPU in the TEL URI format to implement the emergency callback tothe UE. If the PSAP does not support the ENUM function or the PSAP failsto find the IMPU in the SIP URI format of the UE by the ENUM function,thus the PSAP can not obtain the IMPU in the SIP URI format of the UEand can not call back the UE, resulting in a failure in the emergencycallback initiated by the PSAP. For solving the problem, the variousembodiments of the present provide the following methods and systems.

FIG. 2 illustrates a method for establishing an emergency call in an IMSdomain in accordance with an embodiment. The method is described infurther detail below.

In Block 201, a UE sends an emergency call request message to a P-CSCF.The request message contains an emergency identifier, and an IMPU in theTEL URI format or an IMPU in the SIP URI format. The IMPU is containedin the P-Preferred-Identity header of the emergency call requestmessage.

In Block 202, the P-CSCF receives the emergency call request message,then the P-CSCF checks whether the IMPU contained in the emergency callrequest message is in the TEL URI format or in the SIP URI format. Ifthe IMPU is in the TEL URI format, Block 203 is performed. If the IMPUis in the SIP URI format, Block 205 is performed.

In Block 203, the P-CSCF checks whether the IMPU in the TEL URI formatis valid. The IMPU in the TEL URI format is contained in the emergencycall request message. If the IMPU in the TEL URI format is valid, Block204 is performed; if the IMPU in the TEL URI format is not valid, theemergency call fails, and the process is terminated.

In Block 204, the P-CSCF generates a P-Asserted-Identity header in theemergency call request message, and generates an IMPU in the SIP URIformat according to the IMPU in the TEL URI format. The IMPU in the SIPURI format and the IMPU in the TEL URI format are both contained in theP-Asserted-Identity header. Meanwhile, the P-CSCF deletes theP-Preferred-Identity header from the emergency call request message, andthen sends the emergency call request message to an E-CSCF, and Block206 is performed.

The P-CSCF generates the IMPU in the SIP URI format according to theIMPU in the TEL URI format in the following two methods.

In one method, the P-CSCF finds the IMPU in the SIP URI formatassociated with the IMPU in the TEL URI format according to anassociated relation between the IMPU in the TEL URI format and the IMPUin the SIP URI format. The associated relation is saved by the P-CSCFduring a registration process.

In the registration process, an S-CSCF sends a registration responsemessage to the P-CSCF, the registration response message contained aP-Associated-URI header, the P-Associated-URI contains an implicitregistration set of the UE. The implicit registration set contains theIMPU in the TEL URI format of the UE and the IMPU in the SIP URI formatof the UE. The implicit registration set of the UE is saved in theP-CSCF.

In the other method, in the registration process, the P-CSCF parses theSIP URI of the S-CSCF, and obtains a home domain name of the UE. The SIPURI of the S-CSCF is saved by the P-CSCF during the registrationprocess. The P-CSCF obtains an E.164 number of the UE according to theIMPU in the TEL URI format of the UE, and combines the E.164 number ofthe UE with the home domain name of the UE to obtain the IMPU in the SIPURI format of the UE.

For example, the IMPU in the TEL URI format of the UE is: tel:+86-10-8888888, the E.164 number of the UE is: +86-10-8888888. If theSIP URI of the S-CSCF saved in the P-CSCF is: sip:orig@scscf1.home1.net, the home domain name of the UE is “home1.net”.Therefore, the IMPU in the SIP URI format of the UE is: sip:+86-10-8888888@home1.net; user=phone. Where “user=phone” indicates thatthe IMPU in the SIP URI format can be transformed into the IMPU in theTEL URI format equivalently, i.e., the content ahead of the domain nameof the IMPU in the SIP URI format is the E.164 number of the IMPU in theTEL URI format.

In Block 205, the P-CSCF generates a P-Asserted-Identity header in theemergency call request message, and generates an IMPU in the TEL URIformat according to the IMPU in the SIP URI format contained in theemergency call request message. The IMPU in the TEL URI format and theIMPU in the SIP URI format are both contained in the P-Asserted-Identityheader. Meanwhile, the P-CSCF deletes the P-Preferred-Identity headerfrom the emergency call request message, and sends the emergency callrequest message to the E-CSCF.

In the Block 205, the P-CSCF finds the IMPU in the TEL URI format of theUE associated with the IMPU in the SIP URI format of the UE, accordingto the associated relation between the IMPU in the SIP URI format andthe IMPU in the TEL URI format. The IMPU in the SIP URI format of the UEis contained in the emergency call request message sent by the UE. Theassociated relation is saved by the P-CSCF during the registrationprocess.

In Block 206, the E-CSCF forwards the emergency call request message tothe PSAP after receiving the emergency call request message.

In Block 207, the PSAP saves the IMPU in the TEL URI format and the IMPUin the SIP URI format after receiving the emergency call requestmessage. The IMPU in the TEL URI format and the IMPU in the SIP URIformat are contained in the emergency call request message.

In Blocks 208, the PSAP determines to initiate an emergency callback tothe UE.

In Blocks 209, the PSAP checks whether the PSAP itself is located in theCS domain or the PS domain. If the PSAP is in the CS domain, Block 210is performed. If the PSAP is in the PS domain, Block 211 is performed.

In Block 210, the PSAP sends the emergency callback request message tothe UE via the S-CSCF and the P-CSCF in turn according to the IMPU inthe TEL URI format. The IMPU in the TEL URI format is saved in the PSAP.

In Block 211, the PSAP sends the emergency callback request message tothe UE via the S-CSCF and the P-CSCF in turn according to the IMPU inthe SIP URI format. The IMPU in the SIP URI format is saved in the PSAP.

Compared with the prior art, if the IMPU in the TEL URI format isdetected in the emergency call request message sent by the UE, theP-CSCF generates the IMPU in the SIP URI format according to the IMPU inthe TEL URI format, and sends the IMPU in the SIP URI format and theIMPU in the TEL URI format jointly to the PSAP. Therefore, the PSAP inthe PS domain can always acquire the IMPU in the TEL URI format of theUE and the IMPU in the SIP URI format of the UE. If the PSAP does notsupport the ENUM function, it can also initiate an emergency callback tothe UE according to the IMPU in the SIP URI format saved in the PSAP.Consequently, the PSAP in the PS domain will have a much better chanceof successfully initiating an emergency callback. If the PSAP supportsthe ENUM function, it can initiate an emergency callback to the UEdirectly according to the IMPU in the SIP URI format saved in the PSAP,instead of searching for the IMPU in the SIP URI format of the UEthrough the ENUM function, thereby shortening the duration ofestablishing an emergency call.

FIG. 3 illustrates the constitution of the system for establishing anemergency call in the IMS domain in accordance with an embodiment. Thesystem includes a UE 31, a P-CSCF 32, a PSAP 33 and an S-CSCF 34.

The UE 31 sends an emergency call request message to the P-CSCF 32, andreceives an emergency callback request message sent by the P-CSCF 32.The emergency call request message contains an IMPU in the TEL URIformat of the UE or an IMPU in the SIP URI format of the UE.

The P-CSCF 32 receives the emergency call request message sent by the UE31. If the P-CSCF 32 detects that the emergency call request messagecontains the IMPU in the TEL URI format, it generates an IMPU in the SIPURI format according to the IMPU in the TEL URI format. If the P-CSCF 32detects that the emergency call request message contains the IMPU in theSIP URI format, it generates an IMPU in the TEL URI format according tothe IMPU in the SIP URI format. The P-CSCF 32 sends the emergency callrequest message to the PSAP 33, and the emergency call request messagecontains both the IMPU in the SIP URI format and the IMPU in the TEL URIformat. Further, the P-CSCF 32 sends the emergency callback requestmessage which sent by S-CSCF 34 to the UE 31.

The PSAP 33 receives and saves both the IMPU in the SIP URI format andthe IMPU in the TEL URI format which are contains in the emergency callrequest message sent by the P-CSCF 32. When the PSAP 33 determines toinitiate an emergency callback to the UE 31, if the PSAP 33 is locatedin a CS domain, the PSAP 33 sends the emergency callback request messageto the UE 31 via the S-CSCF 34 and the P-CSCF 32 according to the IMPUin the TEL URI format, the IMPU in the TEL URI format is saved in thePSAP 33 itself. If the PSAP 33 is in a PS domain, the PSAP 33 sends theemergency callback request message to the UE 31 via the S-CSCF 34 andthe P-CSCF 32 according to the IMPU in the SIP URI format, the IMPU inthe SIP URI format is saved in the PSAP 33 itself.

The S-CSCF 34 sends the emergency callback request message to the P-CSCF32, the emergency callback request message is sent by the PSAP 33.

FIG. 4 illustrates the schematic diagram of the structure of the P-CSCFin accordance with an embodiment. As shown in FIG. 4, the P-CSCF mainlyincludes an IMPU reception and detection module 41 and an IMPU formatconversion module 42.

The IMPU reception and detection module 41 receives an emergency callrequest message sent by a UE. The emergency call request messagecontains an IMPU. The IMPU reception and detection module 41 sends theIMPU to the IMPU format conversion module 42 if the IMPU is detected inthe TEL URI format. Furthermore, the IMPU reception and detection module41 sends the IMPU to the IMPU format conversion module 42 if the IMPU isdetected in the SIP URI format.

The IMPU format conversion module 42 generates an IMPU in the SIP URIformat according to the IMPU in the TEL URI format which is sent by theIMPU reception and detection module 41, and sends the emergency callrequest message to the PSAP. The emergency call request message containsboth the IMPU in the SIP URI format and the IMPU in the TEL URI format.

Furthermore, the IMPU format conversion module 42 generates an IMPU inthe TEL URI format according to the IMPU in the SIP URI format which issent by the IMPU reception and detection module 41, and sends theemergency call request message to the PSAP. The emergency call requestmessage contains both the IMPU in the TEL URI format and the IMPU in theSIP URI format.

Though illustration and description of the present disclosure have beengiven with reference to various embodiments thereof, it should beappreciated by persons of ordinary skill in the art that various changesin forms and details can be made without deviation from the spirit andscope of this disclosure, which are defined by the appended claims.

1. A method for establishing an emergency call, comprising: receiving,by a Proxy-Call Session Control Function entity, P-CSCF, an emergencycall request message; if the emergency call request message contains anInternet Protocol Multimedia Subsystem Public User Identity, IMPU, in aTelephone Uniform Resource Identifier, TEL URI, format, generating, bythe P-CSCF, an IMPU in a Session Initiation Protocol, SIP, URI formataccording to the IMPU in the TEL URI format; sending, by the P-CSCF, theIMPU in the TEL URI format and the IMPU in the SIP URI format to aPublic Safety Answering Point, PSAP; and receiving, by the P-CSCF, anemergency callback from the PSAP according to the IMPU in the TEL URIformat or the IMPU in the SIP URI format.
 2. The method of claim 1,wherein an associated relation between the IMPU in the TEL URI formatand the IMPU in the SIP URI format is saved by the P-CSCF during aregistration procedure.
 3. The method of claim 2, wherein thegenerating, by the P-CSCF, the IMPU in the SIP URI format according tothe IMPU in the TEL URI format, comprises: searching, by the P-CSCF, inthe associated relation saved in the P-CSCF, for the IMPU in the SIP URIformat associated with the IMPU in the TEL URI format.
 4. The method ofclaim 1, wherein the P-CSCF saves the SIP URI of an S-CSCF during aregistration procedure.
 5. The method of claim 4, wherein thegenerating, by the P-CSCF, the IMPU in the SIP URI format according tothe IMPU in the TEL URI format, comprises: obtaining, by the P-CSCF, theIMPU in the SIP URI format of the UE according to the SIP URI of theS-CSCF and the IMPU in the TEL URI format of the UE.
 6. The method ofclaim 5, wherein the obtaining, by the P-CSCF, the IMPU in the SIP URIformat of the UE according to the SIP URI of the S-CSCF and the IMPU inthe TEL URI format of the UE, comprises: obtaining, by the P-CSCF, anE.164 number of the UE according to the IMPU in the TEL URI format ofthe UE, obtaining, by the P-CSCF, a home domain name of the UE byparsing the SIP URI of the S-CSCF, and combining, by the P-CSCF, theE.164 number of the UE with the home domain name of the UE.
 7. Themethod of claim 1, wherein the emergency callback initiated by the PSAP,comprises: if the PSAP is located in a Circuit-Switched, CS, domain, theemergency callback is initiated by the PSAP according to the IMPU in theTEL URI format saved in the PSAP; and if the PSAP is located in aPacket-Switched, PS, domain, the emergency callback is initiated by thePSAP according to the IMPU in the SIP URI format saved in the PSAP.
 8. Asystem for establishing an emergency call, comprising: a User Equipment,UE, configured to send an emergency call request message to a Proxy-CallSession Control Function, P-CSCF, wherein the emergency call requestmessage contains an Internet Protocol Multimedia Subsystem Public UserIdentity, IMPU, of the UE; the P-CSCF, configured to generate an IMPU ina Session Initiation Protocol, SIP, URI format, where the IMPU of the UEcontained in the emergency call request message received from the UE isin a Telephone Uniform Resource Identifier, TEL URI, format, and sendthe IMPU in the SIP URI format and the IMPU in the TEL URI format to aPublic Safety Answering Point, PSAP; and the PSAP, configured toinitiate an emergency callback to the UE according to one of the IMPU inthe SIP URI format and the IMPU in the TEL URI format received from theP-CSCF.
 9. A Proxy-Call Session Control Function, P-CSCF, comprising: anInternet Protocol Multimedia Subsystem Public User Identity, IMPU,reception and detection module, and an IMPU format conversion module,wherein, the IMPU reception and detection module is configured toreceive an IMPU sent by a User Equipment, UE, and send the IMPU to theIMPU format conversion module if the IMPU is in a Telephone UniformResource Identifier, TEL URI, format; the IMPU format conversion moduleis configured to generate an IMPU in a Session Initiation Protocol, SIP,URI format according to the IMPU in the TEL URI format: and the P-CSCFis further configured to send the IMPU in the SIP URI format and theIMPU in the TEL URI format to a Public Safety Answering Point, PSAP.